physics question about a fairground ride

A fair ground ride comprises of a car, connected to an arm, secured to the main driver by a pin. It rotates about a vertical axis.

when operational:

a) what type of stress is experienced by the pin?, and what type of stress is experienced by the arm?

b) if the max allowable stress in the pin is 15MN/m˛; the pin is 25mm diameter, determine the max force F that the car should exert on the pin.

c)if the loaded mass of the car is 200Kg and the radius from the axis of rotation to the centre of mass of the car is 8m determine the angular velocity of the car about the axis of rotation which will give rise to a stress of 12MN/m˛ in the pin.

Centrifugal force ... F=(m)(r)(w˛)

http://i1152.photobucket.com/albums/...6/P1000106.jpg because the attachments wouldnt work

i think ive got question a sorted, the pin i believe is shear stress and tensile on the arm

b) i believe that to find the force i must use the formula stress=Force/Area and re-arrange it to be Stress X Area = force.

for c) if stress = F/A and using the centrifugal force F=mass x r x angular velocity˛ do i substitute the centrifual force formula into the stress =f/a formula. then rearrange it all so i can work out the angular velocity which the question is asking for?

so Stress = (m.r.w˛)/area of circle

rearranged to: stress x (area of circle)/(mass x radius) =w˛

then square root the answer to get angular velocity?

can anyone just go through it to see if i'm right or wrong please? thanks